I am working this same problem on my friends 2003 330Ci Vert. We ended up finding a short on the bus that powers fuses 1-15. Eventually we pulled fuses 11 & 13 (Roll Over System & Air Bags) and were able to get almost everything back on. Now our symptoms are the Air Bag and Roll Over system lights flicker on the instrument cluster. We also noticed that when the horn is activated it sometimes works... but more interesting is that the flickering Roll Over & Air Bag turn on all the way when the horn is pressed. So I'm thinking that we may have a short in the steering wheel or column. Either a bad clock spring or short wire of some sort. Hopefully we solve this issue cause it seems to be happening more often to other people.
Also make to check Fuse #10 as your symptoms can be caused by a shorted #10 fuse. Keep us posted!
UPDATE!!! PROBLEM FIXED!!!
It ended up being the ignition switch! I swapped out the one I had in my '04 330Ci and put it in her '03 and everything started working properly. We did have to reset the convertible top function but all the other functions & features are working properly. I took apart the faulty ignition switch and took continuity measurements that I will compare against the new ignition switch that I have ordered.
I hope this information helps someone else out. If you are having these similar symptoms please see if pulling fuses 11 & 13 causes these results for you. If so then look toward replacing your ignition switch to solve your problems. Good luck everyone!
2004 BMW 330Ci Convertible
Last edited by Nickvjr; 02-24-2013 at 02:41 AM.